Mileage meters for commercial vehicles such as taxicabs and long-haul trucks are calibrated and certified by governmental agencies for a specific tire pressure and a certain rim size. When the tire pressure and rim size of a vehicle are changed, distance errors of 3 percent can be obtained. For consumers, increased mileage readings by a taximeter increase their costs. For a state governmental agency which taxes a long-haul truck based on the number of miles driven by the long-haul truck within the state, shortened mileage readings result in significant revenue shortfall for the state.
Consequently, a need exists for a technique of calibrating mileage meters, such as taximeters and long-haul truck mileage meters.
A taximeter or mileage meter system which is based exclusively on GPS techniques could theoretically provide accurate distance information and could be continuously calibrated. However, a taximeter or mileage meter using only a GPS system is limited because of outages caused by passage of a vehicle with such a system through tunnels, canyons, dense urban areas, etc.
A taximeter or mileage meter is used to provide distance measurements. U.S. Pat. No. 5,014,206 granted to Scribner et al. on May 7, 1991, and entitled "Tracking System" discloses a system used for determining and recording the geographic location of a vehicle during predetermined events using a GPS system. The Scribner et al. system is adapted to a particular application by configuring a switch or sensor to record the occurrence of a desired event, such as the opening of a garbage truck tailgate at a waste dump site. Passive RF tags are used to identify a vehicle as being at a particular site at a particular time.